The two glycosphingolipids galactosylceramide (GalC) and its sulfated form,
cerebroside sulfate (CBS), are present at high concentrations in the multi
layered myelin sheath and are involved in carbohydrate-carbohydrate interac
tions between the lipid headgroups, In order to study the structure of the
complex of these two glycolipids by Fourier transform infrared (FTIR) spect
roscopy, GalC dispersions were combined with CBS dispersions in the presenc
e and absence of Ca2+. The FTIR spectra indicated that a strong interaction
occurred between these glycolipids even in the absence of Ca2+. The intera
ction resulted in dehydration of the sulfate, changes in the intermolecular
hydrogen bonding interactions of the sugar and other oxygens, decreased in
termolecular hydrogen bonding of the amide C=O of GalC and dehydration of t
he amide region of one or both of the lipids in the mixture, and disorderin
g of the hydrocarbon chains of both lipids. The spectra also show that Ca2 interacts with the sulfate of CBS. Although they do not reveal which other
groups of CBS and GalC interact with Ca2+ or which groups participate in t
he interaction between the two lipids, they do show that the sulfate is not
directly involved in interaction with GalC, since it can still bind to Ca2
+ in the mixture. The interaction between these two lipids could be either
a lateral cis interaction in the same bilayer or a trans interaction betwee
n apposed bilayers. The type of interaction between the lipids, cis or tran
s, was investigated using fluorescent and spin-label probes and anti-glycol
ipid antibodies. The results confirmed a strong interaction between the Gal
C and the CBS microstructures, They suggested further that this interaction
caused the CBS microstructures to be disrupted so that CBS formed a single
bilayer around the GalC multilayered microstructures, thus sequestering Ga
lC from the external aqueous phase. Thus the CBS and GalC interacted via a
trans interaction across apposed bilayers, which resulted in dehydration of
the headgroup and interface region of both lipid bilayers, The strong inte
raction between these lipids may be involved in stabilization of the myelin
sheath.